Cu and Zn Uptake Inhibition by PAHs as Primary Toxicity in Plants
Studies of the interference of polycyclic aromatic hydrocarbons (PAHs) on the uptake of copper (Cu) and zinc (Zn) by alfalfa (Medicago sativa) were investigated. Alfalfa plants were treated with three PAH compounds individually at 50 mg·kg–1(soil dry weight) along with Zn and/or Cu. The concentrations of metals were 35 mg·kg–1(soil dry weight) for Zn and 100 mg·kg–1(soil dry weight) for Cu which levels were associated with the reported concentrations in soils in the El Paso area. Phenanthrene (Phen) and bezo(a)pyrene (BaP) with combination of Zn or/and Cu were found to reduce the size of alfalfa in 5 days of germination/seedling period. Significant decrease in size in alfalfa was 67–91% in 50 mg·kg–1BaP treatments, and 30–75% in 50 mg·kg–1Phen treatments. The uptake of Zn and Cu by alfalfa under the influence of Phen and BaP after 35 days of growth period showed distinctive difference. The Cu uptake was totally inhibited by the two PAHs, while the Zn uptake was inhibited by BaP but enhanced by Phen. Acethylanthracene, however, did not show any effect on the metal uptake. The very different impact of PAH compounds on metal uptake was an indication that there may be various uptake pathways and mechanism of the organics entering into roots.
KeywordsMetal Uptake Acute Toxicity Test Metal Treatment Alfalfa Seed Alfalfa Seedling
The authors gratefully acknowledge the support of HBCU/MI (Historically Black Colleges and Universities/Minority Institutions) under the grant DE-FC0202EW15254, CERM (Center for Environmental Resource Management) at UTEP, CONACYT (Consejo Nacional de Ciencia y Tecnologia), and SRI (Secretaria de Relaciones Internacionales), Mexico.
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